Why might you need more than one? Do you mean more than one instance? Assuming so, provided you aren't subclassing the validator and adding some state other than what is already there, you shouldn't need one.

The existing state just covers bits like 'what is the regex', and 'what error message do we use'. If you customize one, and use the same validator in multiple cases, naturally they will all have the same values, whether or not this is what you intended.

One idea I have as a simple solution would be to make the email address the key for you model that way you would get an exception thrown trying to add a record with the same key. However I sure there's a better way.